Volumetric ultrasound imaging with a thinned array

ABSTRACT

A thinned array of ultrasound transducers includes plural transmitters configured so that each transmitter insonates one segment of a volume at a time and an array of receivers electronically aimed at and dynamically focused upon subsegments of the insonated segment. The spacing between receivers is greater than one-half the transmitted wavelength. Echoes are received in a pattern that is aligned with the insonates segment so that receiver grating lobes nearest the echoes coincide with first transmitter nulls, minimizing the deleterious effects of grating lobes.

BACKGROUND OF THE INVENTION

Conventional ultrasound imaging equipment measures range and only oneangle to produce a two dimensional slice through the organ beingmonitored. Typically, it produces a slice consisting of 256 lines in a{fraction (1/30)} th of a second time frame. For each depth, this gives256 picture elements or pixels per slice, one slice per frame. Thedifficulty that arises in three-dimensional imaging is that N slicesrequire N² lines as opposed to N. A solution is to form many lines at atime.

Three dimensional ultrasound imaging systems currently exist, allowingany slice, at any orientation, to be displayed at the discretion of theuser. For example, a particular system presently available employs atransmitter beam that insonifies a 4 by 4 array of 16 receiver beams.Since 16 beams are formed for each transmitted pulse, 16×256 lines areproduced in each frame. This allows for the formation of a threedimensional image in a single frame, with a 64 by 64 array of pixels foreach depth. However, this array of pixels limits the resolution of any3D image produced with this system.

An ultrasonic device set forth in WO 00/072,756 , which is herebyincorporated by reference in its entirety, provides for far more receivebeams per pulse. In particular, an N by N receiver array described inthe WO 00/072,756 application can provide (N/2)² simultaneous receivebeams. Thus, choosing N=16, for example, produces an 8 by 8 array of 64receiver beams for each transmitted pulse. Moreover, a device of the WO00/072,756 application utilizes a planar array of rectangular ultrasoundtransducer elements comprising multiple transmitters and a thinnedreceiver array (elements are spaced more than ½ wavelength apart). Asubset of the total aperture is used to transmit for a given time andinsonate a number of receive beam positions without insonating thereceiver grating lobes that result from thinning. In order to perform3-dimensional ultrasound imaging, with a meaningful number of lines intwo angular dimensions (called azimuth and elevation), it is necessaryto scan a wide transmit beam so as to cover, say, a 90° sector (±45°) inboth azimuth and elevation.

Thus, a device as described in the WO 00/072,756 application allows fora 128×128 array of pixels for each depth. Furthermore, a device of theWO 00/072,756 application utilizes a thinned array, reducing the numberof array elements and resulting in far less cabling and inputelectronics.

However, a thinned array described in the WO 00/072,756 application haslimited applications in evaluating a large volume of a subject's body.Thus, in order to make such an evaluation, it may be necessary to takedata from a particular segment of the subject's body, and thenphysically move the thinned array to an adjacent segment for additionaldata taking.

Accordingly, what is needed is a thinned array that permitshigh-resolution imaging of a large volume a subject's body, without thenecessity of relocating the array. Such a thinned array would improvethe performance of presently known ultrasound devices, and furtherpermit their use in fields such as cardiac diagnosis and monitoring.

What is also needed is a thinned array that has applications with anypresently available or subsequently discovered ultrasound device.

What is also needed is a thinned array that is configured to suppress,or at least severely limit spatial ambiguities, or “grating lobes” thatwould interfere with the application of an ultrasound device, anddecrease the resolution of a three dimensional image generated fromechoes received from the subject's body.

The citation of any reference herein should not be construed as anadmission that such reference is available as “Prior Art” to the instantapplication.

SUMMARY OF THE INVENTION

There is provided, in accordance with the present invention a novel,useful, and unobvious thinned array for use with an ultrasound device,that offers the advantage of permitting high-resolution imaging of alarge volume of a subject's body.

Broadly, the present invention extends to a thinned array for use withan ultrasound device for evaluating a volume of a subject's body,wherein the volume is formed of a plurality of segments. Such a thinnedarray comprises:

(a) a plurality of transmitters configured so that one transmitterinsonates one individual segment of the volume at a time; and

(b) an array of receivers that simultaneously receive echoes from thevolume being evaluated, wherein the array of receivers is electronicallyaimed and dynamically focused upon sub-segments of the insonated segmentof the volume, wherein the spacing among the receivers in the array isgreater than ½ the wavelength of the ultrasonic energy produced by thetransmitters, and the receivers are configured to receive echoes fromthe sub-segments of the individual insonated segments of the volume ofthe subject's body in a pattern that is aligned with the insonatedsegment of the volume insonated by the transmitters, so that receivergrating lobes nearest the echoes coincide with first transmitter nulls,and the deleterious effects of grating lobes are minimized.

In a particular embodiment, the transmitters and receivers of a thinnedarray of the present invention are in a two-dimensional configuration.The shape of the transmitters can vary. Particular examples include, butcertainly are not limited to rectangles, e.g., a square, and diamondshapes. In an embodiment wherein the transmitters are rectangular inshape, the transmitters are positioned flush against each.

As explained above a thinned array of the present invention alsocomprises a plurality of receivers that simultaneously receive echoesfrom the volume being evaluated, wherein the spacing of the receivers isgreater than ½ the wavelength of the sonic energy produced by thetransmitters. In a particular embodiment of the present invention,wherein the transmitters are diamond in shape, the receivers canoptionally be interleaved with the transmitters.

Naturally, a thinned array of the present invention is electronicallyconnected to a particular ultrasound device utilizing the thinned array.

Thus, a thinned (greater than ½ wavelength element spacing) array ofultrasound transducers of the present invention is used to form a largenumber of received and focused beams within an insonated volume. Sincearray thinning allows for scanning or imaging over only a limited regionor segment, a set of transmitters are fired one at a time to insonateone segment at a time. The receiver is an array of receiver elements,all receiving simultaneously echoes from the volume of the subject'sbody insonated by the transmitters one at a time. A novel aspect of thepresent invention, wherein each particular transmitter insonates asegment of the volume subject's body, permits the insonation andevaluation of a larger volume the subject's body than can be evaluatedwith heretofore known thinned arrays. A large number of receive beamsare formed digitally for each transmitted pulse, and each transmitter isdesigned to provide very little energy in the direction of undesiredreceiver spatial ambiguities or “grating lobes”.

In another embodiment, the present invention extends to a thinned arrayfor use with an ultrasound device for evaluating a volume of a subject'sbody, comprising:

(a) an array of transmitters having spacing that is greater than ½ thewavelength of the ultrasonic energy produced by the transmitters, andthe array of transmitters are configured to insonate sub-segments ofsegments of the volume of the subject's body being evaluated, so thattransmitter grating lobes coincide with first receiver nulls so thatdeleterious effects of grating lobes are minimized, and the arrayelectronically scans the segments of the volume of the subject's bodybeing evaluated, one sub-segment at a time; and

(b) a plurality of receivers that simultaneously receive echoes from thesub-segments of the segments of the volume of the subject beingevaluated, wherein each receiver points to a particular grating lobe ofthe transmitter pattern, or to a particular segment of volume.

Naturally, a thinned array of the present invention is electronicallyconnected to a particular ultrasound device utilizing the thinned array.

Furthermore, the present invention extends to a method for insonating avolume of a subject with a thinned array for use with an ultrasounddevice, comprising the steps of:

(a) providing a thinned array for evaluating a volume of a subject'sbody, the thinned array comprising:

(i) a plurality of transmitters configured so that one transmitterinsonates one individual segment of the volume at a time; and

(ii) an array of receivers that simultaneously receive echoes from thevolume being evaluated, wherein the array of receivers is electronicallyaimed and dynamically focused upon sub-segments of the insonated segmentof the volume, wherein the spacing among the receivers in the array isgreater than ½ the wavelength of the ultrasonic energy produced by thetransmitters, and the receivers are configured to receive echoes fromthe sub-segments of the individual insonated segments of the-volume ofthe subject's body in a pattern that is aligned with the insonatedsegment of the volume insonated by the transmitters, so that receivergrating lobes nearest the echoes coincide with first transmitter nulls,and the deleterious effects of grating lobes are minimized; and

(b) electrically connecting the thinned array to the ultrasound device,so that the volume of the subject can be ultrasonically evaluated.

Moreover, the present invention extends to a method for insonating avolume of a subject with a thinned array for use with an ultrasounddevice, comprising the steps of:

(a) providing a thinned array for evaluating a volume of a subject'sbody, the thinned array comprising:

(i) an array of transmitters having spacing that is greater than ½ thewavelength of the ultrasonic energy produced by the transmitters, andthe array of transmitters are configured to insonate sub-segments ofsegments of the volume of the subject's body being evaluated, so thattransmitter grating lobes coincide with first receiver nulls so thatdeleterious effects of grating lobes are minimized, and the arrayelectronically scans the segments of the volume of the subject's bodybeing evaluated, one sub-segment at a time; and

(ii) a plurality of receivers that simultaneously receive echoes fromthe sub-segments of the segments of the volume of the subject beingevaluated, wherein each receiver points to a particular grating lobe ofthe transmitter pattern, or to a particular segment of volume; and

(b) electrically connecting the thinned array to the ultrasound device,so that the volume of the subject can be ultrasonically evaluated.

Accordingly, it is an object of the present invention to provide a noveland useful thinned array that permits high-resolution imaging of a largevolume a subject's body, without the necessity of relocating the array.

It is another object of the present invention to provide a novel anduseful thinned array that can be readily utilized with any presentlyknown or subsequently developed ultrasound device.

It is yet another object of the present invention to provide a novel anduseful thinned array that is configured to suppress, or at leastsubstantially reduce grating lobes.

These and other aspects of the present invention will be betterappreciated by reference to the following drawings and DetailedDescription.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows two possible N/r by M/s arrays of transmitterscorresponding to an N by M receiver array, illustrated for the CaseN/r=M/s=4. Each square or diamond represents a single transmitter. E.g.,N=M=8 and r=s=2. The rectangular transmitter of FIG. 1A produces the sinx/x Pattem in Azimuth and in Elevation Shown in FIG. 2. FIG. 1B showsthe second, or alternative, transmitter array. The diamond (smallerrotated) transmitters produce a (sin x/x)² pattern in azimuth and inelevation as shown in FIG. 3a.

FIG. 2 shows a two-dimensional sin (2πx)/2πx pattern due to a uniformlyweighted rectangular aperture as in FIG. 1A. Rotating and shrinking theaperture as shown in FIG. 1B rotates and expands the pattern. Theresulting pattern is (sin πx/πx)² in both azimuth and elevation as shownin FIG. 3A. This pattern can also be achieved by applying a triangularshading (amplitude weight taper) across the original (FIG. 1A)rectangular transmitter aperture. By way of example, assume the width(or height) of each transmitter is 2 d, where d is the spacing betweenelements in the N by M rectangular receive array.

FIG. 3 plots one-dimensional patterns for a 16 element linear receivearray and a two-element long transmitter (N=16 and r=2). FIG. 3b shows acluster of eight receiver beams along With the grating lobes of athinned receiver array. FIG. 3a shows the (sin πx/πx)² pattern of atriangularly weighted transmitter. FIG. 3c shows the resultant two-waybeam pattern with grating lobes suppressed. The two-dimensionalcounterpart of FIG. 3 would use an 8×8 array of diamond-shaped uniformlyweighted transmitters and a 16 by 16=256 element planar receive array.This would produce an 8 by 8 cluster of 64 received beams.

FIG. 4 shows the two-way pattern of beam number 8 in FIG. 3C plotted indB. In this case, the grating lobe is suppressed by 12.5 dB.

FIG. 5 shows the beam configuration for 3-D Imaging with (N/2)² by(N/2)² beams formed by (N/2)² Transmissions and an N by N receiverarray, illustrated for the Case of N=16.

FIG. 6 shows an example of interleaving the receiver array elements withthe transmitter array.

DETAILED DESCRIPTION OF THE INVENTION

The present invention is based upon the discovery that surprisingly andunexpectedly, a thinned array for use with an ultrasound device can bedesigned which permits evaluation of a large volume of a subject's body,and increases the number of resolution elements of ultrasound imagesobtained as compared with images obtained with heretofore known arrays.

In an embodiment, the present invention extends to a thinned array foruse with an ultrasound device for evaluating a volume of a subject'sbody, and the thinned array is electrically connected to the ultrasounddevice, the thinned array comprising:

(a) a plurality of transmitters configured so that one transmitterinsonates one individual segment of the volume at a time; and

(b) an array of receivers that simultaneously receive echoes from thevolume being evaluated, wherein the array of receivers is electronicallyaimed and dynamically focused upon sub-segments of the insonated segmentof the volume, wherein the spacing among the receivers in the array isgreater than ½ the wavelength of the ultrasonic energy produced by thetransmitters, and the receivers are configured to receive echoes fromthe sub-segments of the individual insonated segments of the volume ofthe subject's body in a pattern that is aligned with the insonatedsegment of the volume insonated by the transmitters, so that receivergrating lobes nearest the echoes coincide with first transmitter nulls,and the deleterious effects of grating lobes are minimized.

In another embodiment, the present invention extends to a thinned arrayfor use with an ultrasound device for evaluating a volume of a subject'sbody, comprising:

(a) an array of transmitters having spacing that is greater than ½ thewavelength of the ultrasonic energy produced by the transmitters, andthe array of transmitters are configured to insonate sub-segments ofsegments of the volume of the subject's body being evaluated, so thattransmitter grating lobes coincide with first receiver nulls so thatdeleterious effects of grating lobes are minimized, and the arrayelectronically scans the segments of the volume of the subject's bodybeing evaluated, one sub-segment at a time; and

(b) a plurality of receivers that simultaneously receive echoes from thesub-segments of the segments of the volume of the subject beingevaluated, wherein each receiver points to a particular grating lobe ofthe transmitter pattern, or to a particular segment of volume.

Furthermore, the present invention extends to a method for insonating avolume of a subject with a thinned array for use with an ultrasounddevice, comprising the steps of:

(a) providing a thinned array for evaluating a volume of a subject'sbody, the thinned array comprising:

(i) a plurality of transmitters configured so that one transmitterinsonates one individual segment of the volume at a time; and

(ii) an array of receivers that simultaneously receive echoes from thevolume being evaluated, wherein the array of receivers is electronicallyaimed and dynamically focused upon sub-segments of the insonated segmentof the volume, wherein the spacing among the receivers in the array isgreater than ½ the wavelength of the ultrasonic energy produced by thetransmitters, and the receivers are configured to receive echoes fromthe sub-segments of the individual insonated segments of the volume ofthe subject's body in a pattern that is aligned with the insonatedsegment of the volume insonated by the transmitters, so that receivergrating lobes nearest the echoes coincide with first transmitter nulls,and the deleterious effects of grating lobes are minimized; and

(b) electrically connecting the thinned array to the ultrasound device,so that the volume of the subject can be ultrasonically evaluated.

Moreover, the present invention extends to a method for insonating avolume of a subject with a thinned array for use with an ultrasounddevice, comprising the steps of:

(a) providing a thinned array for evaluating a volume of a subject'sbody, the thinned array comprising:

(i) an array of transmitters having spacing that is greater than ½ thewavelength of the ultrasonic energy produced by the transmitters, andthe array of transmitters are configured to insonate sub-segments ofsegments of the volume of the subject's body being evaluated, so thattransmitter grating lobes coincide with first receiver nulls so thatdeleterious effects of grating lobes are minimized, and the arrayelectronically scans the segments of the volume of the subject's bodybeing evaluated, one sub-segment at a time; and

(ii) a plurality of receivers that simultaneously receive echoes fromthe sub-segments of the segments of the volume of the subject beingevaluated, wherein each receiver points to a particular grating lobe ofthe transmitter pattern, or to a particular segment of volume; and

(b) electrically connecting the thinned array to the ultrasound device,so that the volume of the subject can be ultrasonically evaluated.

Numerous terms and phrases are used throughout the instant specificationand appended claims.

As used herein, the phrase “element spacing” or “spacing” can be usedinterchangeably and refer to the distance between the center ofreceivers or transmitters of a thinned array of the present invention.In one embodiment of the present invention described above, the spacingbetween transmitters is greater than ½ the wavelength of ultrasonicenergy produced by the transmitters. In another embodiment describedabove, the spacing between the receivers is greater than ½ thewavelength of the ultrasonic energy produced by the transmitters.

As used herein, the phrase “electronically aimed” with respect to anarray of receivers or transmitters of a thinned array of the presentinvention means that phase shifts or delays are applied to theindividual elements so that a beam is steered or focused on a partiularsegment or sub-segement of the volume of the subject being evaluated.

As used herein, the phrase “dynamically focused” with respect totransducers of a thinned array of the present invention means that thephase shifts can vary with time so as to depend on range or depth.

In addition, the phase “first transmitter nulls” as used herein refersto places nearest the insonated segment of the volume of the subject'sbody being evaluated where the transmitter power is zero or near zero.

As used herein, the phrase “transmitter sidelobe patterns” refers to theangular distribution of transmitted energy outside the segmentintentionally insonated.

As used herein, the terms “transducer” and “element” refer totransmitters and/or receivers of ultrasonsic energy.

Hence, contrary to heretofore known thinned arrays for use withultrasound devices, an embodiment of a thinned array of the presentinvention, as described above, utilizes set of dedicated transmitapertures, each permanently aimed in a different direction. If, forexample, the receive array is to be electronically scanned over theentire 90° by 90° sector, the receiver array elements must bewide-angle, covering an entire octant without significant attenuation.

In another embodiment of a thinned array of the present invention,dedicated receiver apertures are used, and the transmitter array isthinned as described herein.

The present invention may be better understood by reference to thefollowing non-limiting Examples, which are provided as exemplary of theinvention. The following Examples are presented in order to more fullyillustrate the preferred embodiments of the invention. They should in noway be construed, however, as limiting the broad scope of the invention.

EXAMPLE I

For simplicity, assume an example of a square array, where the receiverslie on a N by N grid, at a spacing of d for both the horizontal andvertical directions. In this case, the transmitters illustrated in FIG.1 would each be 2 d wide and 2 d high. High-resolution dynamicvolumetric imaging, could, for example, require a 16 by 16 receiverarray and hence an 8 by 8 array of 64 transmitters (N=16). Thetwo-dimensional amplitude pattern of a 2 d×2 d square transmitteraperture is plotted as a function of x=(d/λ) sin θ and y=(d/λ) sin φ inFIG. 2.

Since the receivers are not directive by themselves, suppression ofgrating lobes must be accomplished entirely by the transmitter pattern.Hence triangular shading is used to produce a low-sidelobe (sin πx/πx)²pattern in both x and y (corresponding to azimuth and elevation) This isillustrated in FIG. 3, (showing azimuth only) for the case of N=16.

For example, if f=4 MHz, then λ=c/f=1.540/4=0.385 mm. Making d slightlyless than 1 mm (so that the receiver array is 1.5 cm by 1.5 cm), resultsin d/λ≈2.5. Thus, in this example, the thinning is five to one,resulting in a reduction in the number of elements in the twodimensional array by a factor of 25.

FIGS. 3 and 4 were created using the following MATLAB program:

x=−2:1/128:2-1/128;

p=pi*x+eps; T=(sin(p)./p).{circumflex over ( )}2;

N=16

n=0:N−1;

xo=−.175:.05:.175;

w=hanning(N);

e=(1/N)*ones N,N)*e;

for k=1:8;

e=exp(j*n′*2*pi*(x−xo(k)));

E(k,:)=(2/N)*w′*e;

TE(k,:)=abs(T).*abs(E(k,:))

end

subplot(311); plot(x,abs(T));

ylabel(‘a. Transmitter Pattern’)

subplot(312); plot(x,abs(E));

ylabel(‘b. Receive Patterns’)

subplot(313); plot(x,TE);

ylabel(‘c. 2-way Pattern’)

figure(2); plot(x,10*log 10(TE(8,:)));

zoom on;

FIG. 3a shows the transmitter pattern as a function of x. FIG. 3b showsthe pattern of a 16 element linear array, using Hanning weighting andsteered to 8 different values of x, with |x|<0.2. This corresponds to an8×8 cluster of 64 receiver beams that are digitally produced for eachtransmitted pulse. Since there are 64 transmitters, each aimed andfocused at a different region, 4096 lines are formed in only 64 pulses.This is ¼ the time it takes a conventional ultrasound imager to produceonly 256 lines. Furthermore, only 256 receiver elements and 64transmitter apertures were used.

The resulting beam cluster is illustrated in azimuth only in FIG. 3c. Ingeneral, the origin (x=0) of FIG. 3 will be translated to correspond tothe azimuth angle of the center of the current transmit beam. FIG. 4plots the rightmost beam of FIG. 3c in dB, to show that the gratinglobes are attenuated by at least 25 dB. FIG. 5 shows the beamconfiguration in two angular dimensions, where FIG. 3c is a horizontalcut through the receiver beams illustrated in FIG. 5. The addition oftime delay or depth (range) results in a 3-D image. The 4 to 1 reductionin imaging time allows for increased volumes per second for 3-D colorflow imaging.

As explained above, conventional imagers view a single slice, withbetween 64 and 256 lines or beams. This invention views a threedimensional volume with a 64 by 64 array of lines in ¼ the time. Thearray, is bistatic. However, the transmitters and the receiver elementscould be interleaved as shown in FIG. 6. Alternatively, the arrays couldbe kept separate and the number of transmitters (and hence the totalnumber of lines) can be doubled by filling in the blank spaces of FIG.1b with another set of (N/2)² elements. By way of example, this doublesthe number of transmit beams in FIG. 5 (left hand side) so that 8192beams are created using only 256 receiver elements. By doubling theoverall size of the transmitter array, a total of 16384 beams can beformed.

The signal processing utilized with a thinned array of the invention canbe, for example, the processing described in the '364 applicationdescribed above. However, a thinned array of the present inventionutilizes a set of electronically-aimed fixed-focus transmitters toextend the region imaged beyond the limit imposed by the necessity toavoid grating lobes of a thinned receive array. Heretofore known thinnedarrays do not utilize electronically-aimed and fixed-focus transmitters.Moreover, note that the expanded angular field being imaged with athinned array of the present invention permits its use for diagnostic,monitoring, and therapeutic applications. Tracking procedures such asthose described in the '364 application can keep the near-field arrayfocused at desired points in 3-D space so as to heat or destroy unwantedtissue, gall stones, kidney stones, etc., or maintain criticalpositioning of the image relative to some other device. Since a 3-Dimage is formed, tracking in three dimensions can also be achievedthrough image correlation.

EXAMPLE II

In the embodiment of the present invention set forth in Example I above,FIG. 3a represents the pattern of one of the transmitters, FIG. 3brepresents a set of digitally-formed simultaneously-received beams usinga thinned receiver array, and FIG. 3c is the product of the two. Bysequentially using different transmitters, a large region can be imaged.

In the embodiment of the present invention set forth in this example,the roles of transmitter and receiver are interchanged. Thus, forpurposes of this embodiment, FIG. 3b illustrates the sequential scanningof a transmit beam (and its grating lobes) using a thinned transmitterarray. Also, for purposes of the embodiment set forth in this example,FIG. 3a illustrates the pattern of one of multiple receivers, designedto each receive signals from only one grating lobe. FIG. 3c (the two-waypattern) is the product of the two. Multiple receivers can all receiveenergy at once, each from a different transmitter grating lobe.

The embodiment set forth in this example has the advantage of requiringless computation because the electronically-steered phased-arraytransmit beams are formed one at a time, while the multiple receiversare fixed-focus.

Many other variations and modifications of the present invention will beapparent to those skilled in the art without departing from the spiritand scope of the present invention. The above-described embodiments are,therefore, intended to be merely exemplary, and all such variations andmodifications are intended to be included within the scope of thepresent invention as defined in the appended claims.

What is claimed is:
 1. A thinned array for use with an ultrasound devicefor evaluating a volume of a subject's body, the thinned array beingelectrically connected to said ultrasound device, said thinned arraycomprising: (a) a plurality of transmitters configured so that onetransmitter insonates one individual segment of said volume at a time;and (b) an array of receivers that simultaneously receive echoes fromsaid volume being evaluated, where said array of receivers iselectronically aimed and dynamically focused upon sub-segments of saidinsonated segment of said volume, wherein said receivers in said arrayhave a spacing that is greater than ½ the wavelength of ultrasonicenergy produced by said transmitters, and said receivers are configuredto receive echoes from said sub-segments of said individual insonatedsegments of said volume of the subject's body in a pattern that isaligned with said insonated segment of the volume insonated by thetransmitters, so that receiver grating lobes nearest the echoes coincidewith first transmitter nulls, and the deleterious effects of gratinglobes are minimized.
 2. The thinned array of claim 1, wherein saidtransmitters and receivers are in a two dimensional configuration. 3.The thinned array of claim 2, wherein said transmitters and receiversare rectangular in shape, and are positioned flush against each other insaid thinned array.
 4. The thinned array of claim 2, wherein saidtransmitters are diamond in shape to reduce transmitter sidelobepatterns, which improves depression of receiver grating lobes.
 5. Thethinned array of claim 4, wherein said receivers are interleaved withsaid transmitters.
 6. A thinned array for use with an ultrasound devicefor evaluating a volume of a subject's body, the thinned array beingelectrically connected to said ultrasound device, the thinned arraycomprising: (a) an array of transmitters having spacing that is greaterthan ½ wavelength of ultrasonic energy produced by said transmitters,wherein the array of transmitters are configured to insonatesub-segments of segments of the volume of the subject's body beingevaluated, so that transnitter grating lobes coincide with firstreceiver nulls so that deleterious effects of grating lobes areminimized, and the array electronically scans the segments of the volumeof the subject's body being evaluated, one sub-segment at a time; and(b) a plurality of receivers that simultaneously receive echoes from thesub-segments of the segments of the volume of the subject beingevaluated, wherein each receiver points to a particular grating lobe ofa transmitter pattern, or to a particular segment of volume.
 7. A methodfor insonating a volume of a subject with a thinned array for use withan ultrasound device, comprising the steps of: (a) providing a thinnedarray for evaluating a volume of a subject's body, the thinned arraycomprising: (i) a plurality of transmitters configured so that onetransmitter insonates one individual segment of the volume at a time;and (ii) an array of receivers that simultaneously receive echoes fromthe volume being evaluated, wherein the array of receivers iselectronically aimed and dynamically focused upon sub-segments of theinsonated segment of the volume, where the receivers in the array have aspacing is greater than ½ wavelength of ultrasonic energy produced bythe transmitters, and the receivers are configured to receive echoesfrom the sub-segments of the individual insonated segments of the volumeof the subject's body in a pattern that is aligned with the insonatedsegment of the volume insonated by the transmitters, so that receivergrating lobes nearest the echoes coincide with first transmitter nulls,and deleterious effects of grating lobes are minimized; and (b)electrically connecting the thinned array to the ultrasound device, sothat the volume of the subject can be ultrasonically evaluated.
 8. Themethod of claim 7 wherein the transmitters and receivers are in a twodimensional configuration.
 9. The method of claim 7, wherein thetransmitters and receivers are rectangular in shape, and are positionedflush against each other in the thinned array.
 10. The method of claim7, wherein the transmitters are diamond in shape to reduce transmittersidelobe patterns, which improves depression of receiver grating lobes.11. The method of claim 10, wherein the receivers are interleaved withthe transmitters.
 12. A method for insonating a volume of a subject witha thinned array for use with an ultrasound device, comprising the stepsof: (a) providing a thinned array for evaluating a volume of a subject'sbody, the thinned array comprising: (i) an array of transmitters isgreater than ½ wavelength of ultrasonic energy produced by thetransmitters, and the array of transmitters are configured to insonatesub-segments of segments of the volume of the subject's body beingevaluated, so that transmitter grating lobes coincide with firstreceiver nulls so that deleterious effects of grating lobes areminimized, and the array electronically scans the segments of the volumeof the subject's body being evaluated, one sub-segment at a time; and(ii) a plurality of receivers that simultaneously receive echoes fromthe sub-segments of the segments of the volume being evaluated, whereineach receiver points to a particular grating lobe of the transmitterpattern, or to a particular segment of the volume; and (b) electricallyconnecting the thinned array to the ultrasound device, so that thevolume of the subject can be ultrasonically evaluated.